1. Field of the Invention
The present invention relates to novel porphyrin-nucleus introduced polymers useful as a reagent for measuring trace metals.
2. Discussion of the Background
Heavy metals are classified as xe2x80x9cindustrial wastes requiring specific managementxe2x80x9d and are subject to various environmental quality standards. There is a demand for a method of easily measuring the concentration of each of various heavy metals existing in rivers, lakes, marshes, sewage or factory effluent. It is common practice to employ atomic absorption spectrometry or inductively coupled plasma emission spectrometry (ICP) to quantitatively determine the concentration of heavy metals. These methods are not satisfactory for general purposes, because they involve problems such as high cost and the necessity of pipe arrangements or exhaust systems. On the other hand, absorption spectrophotometry does not have a cost problem and permits measurement through a relatively simple apparatus. However, because absorption spectrophotometry can be influenced by many substances that exist in a sample but are not intended to be measured, absorption spectrophotometry often requires a pretreatment of the sample to remove these substances.
Porphyrin compounds are calorimetric reagents used in absorption spectrophotometry. To their porphyrin ring, several metals are bonded, thereby forming complexes. These metals are affected by, as well as external factors such as pH, a substituent or functional group on the molecule of the porphyrin compounds.
As a colorimetric reagent, porphyrin compounds involve problems such as poor solubility in water. For improving their properties including water solubility or reactivity with metals, attempts have been made to substitute the reaction center, and to introduce a substituent or functional group in the vicinity thereof, bringing about great effects. In recent years, synthesis of water soluble porphyrins having various substituents or functional groups have been reported (J. Amer. Chem. Soc., 94(1972)4511; J. Amer. Chem. Soc., 93(1971)3162; Inorg. Chem., 9(1970)1757; J. Amer. Chem. Soc., 91(1969)607; and J. Heterocycl. Chem., 6(1969)927). There is also a report on the application of these porphyrins to analysis of metals contained at a trace level (ppb level) by making use of a change in fluorescence after formation of a complex with various metals (Analytica Chimica Acta, 74(1975)53-60; J. Japan Chemical Soc., 1978, (5), 686-690; J. Japan Chemical Soc., 1979, (5), 602-606; BUNSEKI KAGAKU vol. 25(1976)781; Japanese patent application laid-open Nos. 082285/95 and 054307/80).
Under the above-described techniques, however, it is necessary to introduce substituents or functional groups to a porphyrin ring in order to impart the porphyrin compound with water solubility or to change reactivity with a metal. An object of the present invention is therefore to provide porphyrin compounds having desired properties or reactivity even by making use of easily available porphyrin compounds xe2x80x9cas isxe2x80x9d, that is, without any modification. The porphyrin compounds of the present invention are useful as a reagent for measuring heavy metals.
With the foregoing in view, the present inventors have found that by performing radical copolymerization of a specific porphyrin compound and a radically polymerizable monomer, thereby introducing the porphyrin nucleus into the main chain of the polymer having various side chains, and, at this time, selecting the proper radically polymerizable monomer, various porphyrin-nucleus introduced polymers different in the stereostructure in the periphery of the porphyrin nucleus without using a porphyrin derivative in which various substituents or functional groups are introduced in the periphery of the porphyrin nucleus are available. They have also found that since the resulting polymers differ in properties including water solubility and also in reactivity with a metal upon complex formation, depending on the structure of the selected radically polymerizable monomer, the polymers are useful as a reagent for measuring a trace metal. As a result, they have completed the present invention.
The present invention thus provides a porphyrin-nucleus introduced polymer obtained by radical copolymerization of a porphyrin compound represented by the following formula (1) or (2): 
wherein, R represents a hydrogen atom or a C1-6 alkyl group, with a radically polymerizable monomer; and a reagent for measuring a trace metal, which contains the polymer.
The novel porphyrin-nucleus introduced polymers according to the present invention are different in properties such as water solubility and also in reactivity with a metal upon complex formation, depending on a radically polymerizable monomer selected as a raw material so that they are useful as a reagent for measuring trace metals or as an agent for removing trace metals.